The goal of this project is to determine the physiological significance of acetylcholine (ACh) in the heart. Using a very sensitive and specific method for ACh analysis, we will examine the effects of bagotomy, sympathectomy, and other experimental maneuvers of the levels of ACh in various areas of cat heart. Information gathered from these studies should add to our understanding of two controversal areas of cardiac physiology: parasympathetic innervation of the ventricles, and the Burn and Rand hypothesis. The knowledge gained from these studies will contribute to the achievement of a comparative concept of nervous control of the heart. BIBLIOGRAPHIC REFERENCE: Brown, Oliver M.: Cat Heart Acetylcholine: Structural Proof and Distribution. Amer. J. Physiol. 231: 781-785, 1976.